Charge transfer effects on Fe 2p X-ray photoemission of RbMn[Fe(CN) ₆], K₃Fe(CN)₆, and K4Fe(CN)₆

In the studies on the valence transition in RbMn[Fe(CN)₆], the Fe valence was determined by observing the binding energy of the primary Fe 2p photoemission line, while the detailed analysis of the whole Fe 2p X-ray photoemission spectrum (XPS) has not so far been performed both experimentally and theoretically. In the present study, the Fe 2p XPS is calculated for [Fe(CN)₆]^3- and [Fe(CN)₆]^4- cluster models by a configuration-interaction full-multiplet theory. The result shows that the line shape of the Fe 2p XPS is affected by ligand-to-metal charge transfer (LMCT) and intraatomic multiplet coupling. It is in clear contrast to the Fe 2p X-ray photoabsorption spectrum (XAS), where metal-toligand charge transfer (MLCT) plays an important role. It is clearly shown that the difference in the ground-state wavefunction between the [Fe(CN)₆]^3- and [Fe(CN)₆]^4- clusters is reflected in the CT satellite structures and the multiplet structures in the Fe 2p XPS. From the analysis of the observed Fe 2p XPS, together with the analysis of the Fe 2p XAS, we conclude that the Fe 3d energy level relative to the C 2p energy level in RbMn[Fe(CN)₆] is considerably larger than that in K ₃Fe(CN)₆.